Magnetic Disk Case

ABSTRACT

A plurality of band shaped projections are formed in parallel on the interior surfaces of side walls of a magnetic disk case so that grooves are formed in spaces between the projections. Each of the grooves has bottom surface A, a pair of side surfaces B, and inclined surfaces C formed between each surface B and the surface A. The grooves satisfies d≦a; w&gt;t; and 2α≦β, where t is a thickness of a magnetic disk, d is a width of a circumferential surface of the magnetic disk subjected to chamfering, α is a chamfer angle, a is a width of the surfaces A, β is an angle between the surfaces C on either side of each groove, γ is an angle between the surfaces B, and w is a shortest distance between the surfaces B on either side of each groove.

TECHNICAL FIELD

The present invention relates to a case for magnetic disks. Priority isclaimed on Japanese Patent Application No. 2004-222810, filed Jul. 30,2004, the content of which is incorporated herein by reference.

BACKGROUND ART

In the prior art, Patent Reference 1 (Japanese Unexamined PatentApplication, First Publication No. S60-90172) discloses a constitutionof a magnetic disk case in which a box having a pair of opposing sidewalls along their length, and grooves in the side walls for storingmagnetic disks, and of which an upper part and a bottom part are open iscombined with an upper lid and a bottom lid placed upon the box.

Upon the inner surfaces of the pair of long side walls of this magneticdisk case, a plurality of grooves for storing magnetic disks are formedin parallel along the length direction of the walls. Specifically, thegrooves of this magnetic disk case are made by forming a plurality oflong thin band shaped projections extending in the upwards and downwardsdirection from the inner surfaces of the pair of long side walls, spacedin a parallel array at intervals along their length; and a plurality ofmagnetic disks can be stored on these left and right pairs of grooves.

When storing and transporting magnetic disks in the magnetic disk case,lids are put upon the top and bottom of this case so that, along withpreventing the ingress of dust, the magnetic disks are lightly pressedby the upper lid so that they do not move, in order that dust should notbe generated by abrasion between the case and the magnetic disks due tomovement of magnetic disks within the case during transportation.

With regard to magnetic disks, it is disclosed to prevent the generationof dust by interposing curved surfaces between the side surfaces ofexternal circumferential end surfaces and chamfers, and between theglass substrate main surfaces and chamfers of the magnetic disks (forexample in Patent Reference 2: Japanese Unexamined Patent Application,First Publication No. 2002-100031).

As described above, when storing and transporting magnetic disks withina magnetic disk case, the magnetic disks are lightly pressed by theupper lid, so that the magnetic disks do not move easily due tovibration during transportation. Furthermore, a chamfering or the likeis performed upon the end surfaces of the magnetic disks, so that itbecomes difficult for dust to be created.

However, there is a problem that, even if this type of countermeasure istaken, when opening and closing the upper lid, or when taking a disk outfrom the case and putting it back in, the disk and the inner surface ofthe case may rub together, and a small amount of dust may be therebycreated, and this dust may adhere to the magnetic recording surface, soas to cause damage to a head of a hard disk device, or to the magneticrecording medium. Furthermore, the increasing recording densities ofmagnetic recording mediums, now require elimination of dust particles ofa level which did not constitute a problem in the prior art.

In order to solve these problems, the objective of the present inventionis to provide a magnetic disk case which reduces the generation of dust.

DISCLOSURE OF INVENTION

The present invention relates to the following:

(1) A magnetic disk case which comprises:

a case main body having a pair of opposing side walls, an open upperpart, and an open bottom part;

an upper lid detachably fitted to the upper part of the case main body;and

a bottom lid detachably fitted to the bottom part of the case main body.

A plurality of band shaped projections (ribs) are formed in parallel onthe interior surfaces of the side walls in a length direction of theside walls so that grooves for holding magnetic disks are formed inspaces between the band shaped projections.

Each of the grooves has bottom surface A, a pair of side surfaces B, andinclined surfaces C formed between each side surface B and the bottomsurfaces A.

The grooves satisfies relations given by:

d≦a,

w>t, and

2α≦β,

where t is a thickness of a magnetic disk to be stored in the magneticdisk case, d is a width of a circumferential surface of the magneticdisk subjected to chamfering, α is a chamfer angle, a is a width of thesurfaces A, β is an angle between the surfaces C on either side of eachgroove, γ is an angle between the surfaces B on either side of eachgroove, and w is a shortest distance between the surfaces B on eitherside of each groove.

(2) A magnetic disk case as described in (1), wherein(2α+10°)≦β≦(2α+30°) is satisfied.(3) A magnetic disk case as described in (1) or (2), wherein 100°≦β≦120°is satisfied.(4) A magnetic disk case as described in any one of (1) to (3), wherein20°≦γ≦40° is satisfied.(5) A magnetic disk case as described in any one of (1) to (4), wherein(d×1.05)≦a≦(d×1.5) is satisfied.

By the use of the magnetic disk case of the present invention, it ispossible to reduce the adhesion of dust generated by abrasion betweenthe magnetic disk and the magnetic disk case to the magnetic disk. Inparticular, since it becomes difficult for the dust to adhere to themagnetic recording surface, it is possible to reduce damage to the headof a hard disk device or to the magnetic recording medium due to dustadhering to the magnetic recording surface, and, furthermore, it becomespossible to provide a magnetic recording medium to which can be appliedan increase in recording density.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic figure showing the magnetic disk case of thepresent invention.

FIG. 2 is a schematic figure of the magnetic disk case of the presentinvention with the upper lid and the bottom lid removed.

FIG. 3 is a sectional view of the magnetic disk case of the presentinvention with a magnetic disk inserted into it.

FIG. 4A is a sectional view showing the positional relationship betweenthe grooves of the magnetic disk case of the present invention, and asubstrate or a magnetic disk.

FIG. 4B is a sectional view showing the shape of the substrate or themagnetic disk.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, appropriate embodiments of the present invention willbe explained with reference to the drawings.

FIGS. 1 through 3 are figures showing the magnetic disk case. Themagnetic disk case 4 is comprised of a case main body 1 having a pair ofside walls, an open upper part, and an open bottom part; a removableupper lid 2 fitted to the upper part of the main body 1, and a removablebottom lid 3 fitted to the bottom part of the main body.

In FIG. 2, grooves 5 are formed by a plurality of band shapedprojections 6 which are formed in parallel along the length of the innersurfaces of a pair of opposing side walls of a case main body 1 of whichthe upper part and the bottom part are left open. It should beunderstood that although, in FIG. 2, two of the band shaped projections6 and the one of the grooves 5 defined by them are shown, in actualpractice, a plurality of these band shaped projections and grooves isformed in the direction of 7.

The positional relationship between the grooves of the magnetic diskcase of the present invention and the substrates or magnetic disks willbe explained using FIGS. 4A and 4B. In FIGS. 4A and 4B, 10 denotes thecross sectional shape of a magnetic disk, while 11 is the crosssectional shape of a groove. Each of the grooves has bottom surface A, apair of side surfaces B, and inclined surfaces C formed between eachside surface B and the bottom surfaces A.

With the magnetic disk case of the invention, the grooves satisfies,d≦a; w>t ; and 2α≦β, where t is a thickness of a magnetic disk 10 to bestored in the magnetic disk case, d is a width of a circumferentialsurface of the magnetic disk subjected to chamfering, α is a chamferangle, a is a width of the surfaces A, β is an angle between thesurfaces C on either side of each groove, γ is an angle between thesurfaces B on either side of each groove, and w is a shortest distancebetween the surfaces B on either side of each groove.

In the present invention, where the edge created by the chamfer processon the side closer to the magnetic recording surface is taken as X, theedge on the side remote from the magnetic recording surface is taken asY, by ensuring that X does not come into contact with the side surfaceof the magnetic disk case, it is made difficult for dust generated byabrasion between magnetic disks and the magnetic disk case to adhere tothe magnetic recording surface.

In other words, by setting the positional relationship between themagnetic disk and the magnetic disk case to a relationship given by theabove described equations, only Y is allowed to come into contact withthe magnetic disk case, while X does not come into contact with themagnetic disk case, and it accordingly becomes difficult for dustgenerated by abrasion between the magnetic disk and the magnetic diskcase to adhere to the magnetic recording surface. The reason for this isthat, by contrast to the edge X contacting with the magnetic recordingsurface, the edge Y does not contact with the magnetic recordingsurface, so that the probability is lowered that dust generated byabrasion between the edge and the magnetic disk case should adhere tothe magnetic recording surface.

Preferably, the magnetic disk case may satisfy 2α+10°≦β≦2α+30°.

This is because, by making α and β be within the above described range,it is possible to prevent contact between the side surfaces of thegrooves and the edge close to the data surface of the disk caused byopening and closing of the upper lid, taking disks out from the case andputting them in, or by vibration generated by shifting of the casewithout the upper lid on it, thus obtaining the beneficial effect ofpreventing dust generated by abrasion between the disk and the case fromadhering to the magnetic recording surface.

More preferably, the magnetic disk case may satisfy 100°≦β≦120°.

Although a chamfer angle of the magnetic disk or magnetic disk substratemay be determined freely, a chamfer angle of 45° is generally employed.Therefore, when the case satisfies the above equation, a case of thesame shape can be widely used for many different types of magnetic disksor magnetic disk substrates, and common use of the case is enabled.

Preferably the magnetic disk case may satisfy 20°≦γ≦40°.

By setting γ within the above described range, disks may be smoothlytaken out of or put in the case, large movement of disks in the lengthdirection of the case is reduced, and contact of directly adjoiningdisks is prevented. If γ is smaller than the above described range, itis undesirable, since the width of the uppermost portion of the groovebecomes small, and, when taking out or putting in a disk, the diskeasily contacts the band shaped projection of the case side walls, andthe possibility of generation of dust is increased. On the other hand,if γ is greater than the above described range, it is undesirable,because the height of the band shaped projection of the case side wallsbecomes small, and when taking out or putting in a disk, it becomes easyto put it into a neighboring groove, and it becomes easy, when shock hasbeen applied to the case, for a disk which has been inserted into thegroove to undergo positional displacement, and for neighboring disks tocome into contact with one another.

Preferably the magnetic disk case may satisfy d×1.05≦a≦d×1.5.

By setting a and b within the above described range, vibration of thedisk in the stored state is minimized, and the edge close to the diskdata surface is protected from contact with the side surface of thegroove.

Preferably, the magnetic disk case described above may be made of anantistatic synthetic resin composed of thermoplastic resin elements. Forexample, polycarbonate resin which has been endowed with electricalconductivity by the admixture of carbon powder, ABS resin, propylenetype resin, PEEK resin, or the like may be used in an appropriatemanner; and, among these, the use of a polycarbonate resin isparticularly preferable.

EXAMPLE 1

Magnetic disk cases were manufactured in which magnetic disks ofdiameter 48 mm (1.89 inch) were to be stored. The cases were made ofpolycarbonate resin endowed with electrical conductivity by theadmixture of carbon powder. The thickness (t) of the magnetic disks wasmade to be 0.508 mm, the chamfer angle (α) was made to be 45°, and thewidth (d) after the chamfering process was made to be 0.268 mm. Withregard to the shape of the grooves of the magnetic disk cases, the width(a) of the surface A was made to be 0.30 mm, the angle (β) between thesurface surfaces C on either side of each groove was made to be 110°,the angle (γ) between the surfaces B on either side of the groove wasmade to be 30°, and the minimum distance (w) between the surfaces B ofeither side of the groove was made to be 1.2 mm.

Fifty magnetic disks were inserted into two of these magnetic disk cases(25 magnetic disks per case), and, after having opened and closed theupper lid five times, the number of dust particles adhering to themagnetic recording surfaces of the fifty magnetic disks was counted. Nodust was observed in an observation using an optical microscope at onehundred times magnification.

COMPARATIVE EXAMPLE 1

The same experiment was performed using magnetic disk cases ofconventional type. The cases were made of the same polycarbonate resinas that of example 1. The grooves of these conventional magnetic diskcases had surfaces corresponding to the surfaces A and B of the presentinvention, but not the surfaces C. Furthermore, the surface A was plane,and the width of the surface A was 0.74 mm, while the angle between thesurfaces B on either side of each groove was 30°.

Using two magnetic disk cases of this type, the same experiment as forexample 1 was performed, and as a result, a total of ten dust particleswas observed upon the magnetic recording surfaces.

EXAMPLE 2

A magnetic disk case was manufactured in which magnetic disks ofdiameter 48 mm (1.89 inch) were to be stored. The cases were made ofpolycarbonate resin endowed with electrical conductivity by theadmixture of carbon powder. The thickness (t) of the magnetic disks wasmade to be 0.508 mm, the chamfer angle (α) was made to be 45°, and thewidth (d) after the chamfering process was made to be 0.268 mm.Furthermore, with regard to the shape of the grooves of the magneticdisk case, the width (a) of the surface A was made to be 0.30 mm, theangle (β) between the surfaces C on either side of each groove was madeto be 100°, the angle (γ) between the surfaces B on either side of thegroove was made to be 30°, and the minimum distance (w) between thesurfaces B of either side of the groove was made to be 1.0 mm.

Twenty-five magnetic disks were inserted into one of these magnetic diskcases (25 magnetic disks per case), and, after taking the disks out andputting them in twenty times, the number of dust particles adhering tothe magnetic recording surfaces of the twenty-five magnetic disks wascounted. No dust was observed in an observation using an opticalmicroscope at one hundred times magnification.

COMPARATIVE EXAMPLE 2

The same experiment was performed using a magnetic disk case ofconventional type. The case was made of the same polycarbonate resin asthat of example 2. The grooves of this magnetic disk case used in thepast had surfaces corresponding to the surfaces A and B of the presentinvention, but not the surfaces C. Furthermore, the surface A was aplane, and the width of the surface A was 0.74 mm, while the anglebetween the surfaces B on either side of each groove was 30°.

Using one magnetic disk case of this type, the same experiment as forexample 2 was performed, and as a result, a total of twenty dustparticles was observed upon the magnetic recording surfaces.

EXAMPLE 3

A magnetic disk case was manufactured in which magnetic disks ofdiameter 48 mm (1.89 inch) were to be stored. The case was made ofpolycarbonate resin endowed with electrical conductivity by theadmixture of carbon powder. The thickness (t) of the magnetic disks wasmade to be 0.508 mm, the chamfer angle (α) was made to be 45°, and thewidth (d) after the chamfering process was made to be 0.268 mm. Withregard to the shape of the grooves of the magnetic disk case, the width(a) of the surface A was made to be 0.30 mm, the angle (β) between thesurfaces C on either side of each groove was made to be 100°, the angle(γ) between the surfaces B on either side of each groove was made to be30°, and the minimum distance (w) between the surfaces B of either sideof the groove was made to be 1.0 mm.

Using one of these magnetic disk cases, and one magnetic disk, and afterhaving taken the latter out and put it back in once so that it wasforcibly contacted against the groove, the number of dust particlesadhering to the magnetic recording surface of this magnetic disk wascounted. This operation was performed in the same manner with threemagnetic disks. No dust was observed in an observation using an opticalmicroscope at one hundred times magnification.

COMPARATIVE EXAMPLE 3

The same experiment was performed using a magnetic disk case ofconventional type. The case was made of the same polycarbonate resin asthat of example 3. The grooves of this conventional magnetic disk casehad surfaces corresponding to the surfaces A and B of the presentinvention, but not the surfaces C. Furthermore, the surface A was aplane, and the width of the surface A was 0.74 mm, while the anglebetween the surfaces B on either side of each groove was 30°.

Using one magnetic disk case of this type, the same experiment as forexample 3 was performed, and as a result, a total of thirty-two dustparticles was observed upon the magnetic recording surface.

INDUSTRIAL APPLICABILITY

By the use of the magnetic disk case of the present invention, it ispossible to reduce the adhesion of dust generated by abrasion betweenthe magnetic disk and the magnetic disk case to the magnetic disk. Inparticular, since it becomes difficult for dust to adhere to themagnetic recording surfaces, it is possible to reduce damage to the headof a hard disk device or to a magnetic recording medium caused by dustadhering to the magnetic recording surface, and it becomes possible toprovide a magnetic recording medium to which can be applied an increasein recording density.

1. A magnetic disk case comprising: a case main body having a pair ofopposing side walls, an open upper part, and an open bottom part; anupper lid detachably fitted to the upper part of the case main body; anda bottom lid detachably fitted to the bottom part of the case main body,wherein a plurality of band shaped projections are formed in parallel onthe interior surfaces of the side walls in a length direction of theside walls so that grooves for holding magnetic disks are formed inspaces between the band shaped projections, each of the grooves hasbottom surface A, a pair of side surfaces B, and inclined surfaces Cformed between each side surface B and the bottom surfaces A, and thegrooves satisfies relations given by:d≦a,w>t, and2α≦β, where t is a thickness of a magnetic disk to be stored in themagnetic disk case, d is a width of a circumferential surface of themagnetic disk subjected to chamfering, α is a chamfer angle, a is awidth of the surfaces A, β is an angle between the surfaces C on eitherside of each groove, γ is an angle between the surfaces B on either sideof each groove, and w is a shortest distance between the surfaces B oneither side of each groove.
 2. A magnetic disk case according to claim1, wherein (2α+10°)≦β≦(2α+30°) is satisfied.
 3. A magnetic disk caseaccording to claim 1, wherein 100°≦β≦120° is satisfied.
 4. A magneticdisk case according to claim 1, wherein 20°≦γ≦40° is satisfied.
 5. Amagnetic disk case according to claim 1, wherein (d×1.05)≦a≦(d×1.5) issatisfied.